Fix JSON payload

get_data.py

@@ -1,6 +1,7 @@
 """
 Read Xiaomi LYWSD03MMC advertised packets and send them to MQTT
 """
+import json
 import os
 from socket import gaierror
 from typing import TypedDict
@@ -54,7 +55,7 @@ def send_to_mqtt(data: MQTTdata) -> None:
         },
         {
             "topic": "sensors/home/{data['mac']}/tele/SENSOR",
-            "payload": data,
+            "payload": json.dumps(data),
         },
     ]